1. Field of the Invention
Embodiments of the invention relate to ocean bottom seismic surveying using seismic sensors deployed at the bottom of the sea. More particularly, embodiments of the invention relate to a seismic station housing in an ocean bottom seismic surveying system using an ocean bottom deployed seismic cable with seismic stations along its length.
2. Background and Prior Art
Seismic surveying using fiber optic technology has recently received attention. Optical based sensors for performing the surveying can include a hydrophone and geophones. These sensors can be fabricated, for example, using Michelson interferometers.
A general problem of arranging a hydrophone together with a three-axis geophone or accelerometer in a four-component seismic sensing station is the cross sensitivity between the hydrophone and the geophones/accelerometers. While it is generally desirable to optimize the exposure of the hydrophone to pressure variations, it is generally undesirable to let pressure variations influence the geophones. The influence of the pressure signal on the geophones/accelerometers creates an undesirable cross sensitivity.
Other potential problems exist with arrangements in the four-component seismic sensing station. One problem of mounting geophones/accelerometers inside an air-filled pressure sealed housing involves mechanical resonances in the geophones/accelerometers. Integrating several fiber optic sensors along a fiber loop in subsea environments creates other limitations relating to connecting arrangements, which require high pressure penetrators for guiding a fiber between low pressure surroundings and high pressure surroundings, and vice versa.
Therefore, there exists a need for an improved seismic sensor station for arranging a hydrophone and one or more geophones.